Israel stepped up its campaign against Gaza's ruling Hamas on Thursday, killing three of the group's senior military commanders in an air strike that pulverized a four-story home, the second such attack targeting top leaders in two days.

The pinpoint pre-dawn attack on Hamas' inner sanctum was launched minutes after the men emerged from tunnel hideouts, a security official said - displaying the long reach of Israel's intelligence services.

The killing of the commanders, who played a key role in expanding Hamas' military capabilities in recent years, was bound to lower morale in the secretive group, but might not necessarily diminish its ability to fire rockets at Israel.

Thursday's strike in the southern Gaza town of Rafah, coupled with a Cabinet decision to call up 10,000 more reserve soldiers, signaled an escalation in the Israel-Hamas war after Egyptian cease-fire efforts collapsed this week.

Since July 8, fighting has claimed more than 2,000 Palestinian lives, most of them civilians, according to Palestinian officials and the U.N., and entire neighborhoods of Gaza have been destroyed. Sixty-four Israeli soldiers, two Israeli civilians and a guest worker also have been killed.

Meanwhile, a senior Hamas leader in exile admitted that Hamas was behind the kidnapping and killing of three Israeli teens in the West Bank - the group's first claim of responsibility for the June attack that triggered an Israeli crackdown and eventually led to the Gaza war.

Saleh Arouri told an international conference of Islamic scholars in Turkey on Wednesday that Hamas grabbed the teens in hopes of sparking a Palestinian uprising in the West Bank.

This week's resumption of Gaza fighting came after several failed rounds of indirect talks of Israel and Hamas in Cairo.

Egyptian mediators had proposed that in exchange for quiet on the Israel-Gaza border, Israel gradually ease a border blockade it had imposed on Gaza, alongside Egypt, after Hamas seized the territory in 2007. Hamas rejected the proposal, saying Israel didn't offer anything specific.

In an apparent attempt to revive diplomacy, Western-backed Palestinian President Mahmoud Abbas held talks in Qatar on Thursday with his main Palestinian rival Khaled Mashaal, the top Hamas leader in exile.

Abbas lost control of Gaza in the Hamas takeover seven years ago, but several months ago signed a reconciliation deal with Hamas that was to give him a new foothold in the territory.